Cellular communication systems are becoming increasingly more important. In such cellular communication systems, a user equipment (UE), such as a mobile phone or cellular computer modems, connects wirelessly to the network via base stations (BSs), that in turn are connected to a backhaul network for forwarding the communication from the user equipment.
An example of such a cellular communication system is the 3GPP (3rd Generation Partnership Project) Long Term Evolution (LTE) system, in the following referred to simply as “LTE”. In LTE, multiple access is achieved using OFDMA (Orthogonal Frequency Division Multiple Access), in which different resource blocks (RBs) can be reserved for different UEs. An RB is built up by a number of sub carriers of an OFDM (Orthogonal Frequency Division Multiplexing) signal during a certain time interval. Duplex communication between a UE and a base station can be accomplished using frequency division duplex (FDD), wherein signals are sent from the UE to the BS in an up-link (UL) frequency band and signals are sent from the BS to the UE in a down-link (DL) frequency band (separate and disjoint from the UL frequency band).
In order to better utilize the resources of a cellular communication system, it has been suggested that UEs may engage in so called device-to-device (D2D) communication, wherein the UEs communicate data directly between them, i.e. without sending the data via the cellular communication network. Such D2D communication may be possible when two UEs are in the proximity of each other. Some aspects of D2D communication are briefly discussed in G Fodor et al, “Design aspects of network assisted device-to-device communications”, IEEE Communications Magazine, pp 170-177, March 2012.
In general (for example for UEs for cellular communication systems capable of D2D communication), there is a desire to develop radio transceiver circuitry that can be manufactured and/or operated at a relatively low cost, such as in terms of circuit area, component count, and/or power consumption. For example, it is generally desired that the bill-of-material associated with introducing support of additional features (such as D2D communication) is kept relatively low.